紫云英还田与化肥减量配施对稻田土壤细菌群落组成和功能的影响

Effects of Chinese Milk Vetch Returning Incorporated with Chemical Fertilizer Reduction on the Composition and Function of Soil Bacterial Communities in Paddy Fields

紫云英是豫南稻区土壤培肥的重要有机肥资源,探究紫云英还田与化肥减量配施对稻田土壤理化性质和细菌群落特性的影响,旨在为该区域的土壤培肥和化肥减量提供依据.开展连续12 a田间定位试验,设置了6个施肥处理(空白对照,CK;单施化肥,F100;80%化肥和22.5t·hm^(-2)紫云英还田量配施,MV1F80;80%化肥和45 t·hm^(-2)紫云英还田量配施,MV2F80;60%化肥和22.5 t·hm^(-2)紫云英还田量配施,MV1F60;60%化肥和45 t·hm^(-2)紫云英还田量配施,MV2F60).通过采用高通量测序方法比较不同施肥处理对土壤细菌群落多样性、组成和结构特性的影响;采用FAPROTAX功能预测的方法分析不同施肥处理间功能类群的丰度差异,并结合土壤理化性质,探究改变土壤细菌群落结构与功能特性的关键土壤环境因子.结果表明,紫云英还田与化肥减量配施降低了土壤容重,提高了土壤有机碳(SOC)、全氮(TN)、全磷(TP)和全钾(TK)含量,较CK提高的范围分别为12.7%~35.5%、38.2%~65.7%、66.7%~95.2%和20.3%~31.6%.紫云英还田与化肥减量配施处理较F100处理降低了细菌Sobs指数和Shannon多样性指数,且Sobs指数和Shannon多样性指数均与容重(BD)呈显著正相关(P<0.05),而与SOC和TN呈显著负相关(P<0.05).MV1F80和MV2F60处理的厚壁菌门(Firmicutes)的相对丰度较F100处理分别提高了82.2%和67.4%(P<0.05),而酸杆菌门(Acidobacteria)的相对丰度分别减少了32.6%和40.5%(P<0.05),仅MV2F60处理放线菌门(Actinobacteria)的相对丰度提高了30.0%(P<0.05).RDA分析表明,土壤SOC、TN和TK是显著影响细菌群落结构变化的主要土壤环境因子(P<0.05).紫云英还田与化肥减量配施处理还提高了化能异养类、固氮类、发酵类和尿素分解类功能类群丰度,降低了动物寄生或共生类、人类所有病原体和人类病原体肺炎类功能类群丰度,其中MV1F80和MV2F60处理效果较好.综上所述,长期的紫云英还田与化肥减量配施改善了土壤理化性质,进而改变了土壤细菌群落结构与功能特性,有助于稻田土壤肥力的提升、微生态系统的稳定和健康,进而保障区域农业的绿色可持续发展.

Chinese milk vetch(Astragalus sinicus L.)is an important organic nutrient resource in the southern Henan rice-growing area.Thus,the effects of Chinese milk vetch(MV)returning incorporated with reduced chemical fertilizer on the physicochemical properties and bacterial community characteristics in paddy soil were studied.These results can provide a certain theoretical basis for the improvement of soil fertility and reduction of chemical fertilizer in this area.A field experiment was conducted for 12 consecutive years,involving six fertilization treatments(blank control,CK;100%chemical fertilizer,F100;80%chemical fertilizer+22.5 t·hm^(-2) MV,MV1F80;80%chemical fertilizer+45 t·hm^(-2) MV,MV2F80;60%chemical fertilizer+22.5 t·hm^(-2) MV,MV1F60;and 60%chemical fertilizer+45 t·hm^(-2) MV,MV2F60).The high-throughput sequencing method was used to compare the effects of different fertilization treatments on soil bacterial community diversity,composition,and structural characteristics.The FAPROTAX function prediction method was used to analyze the abundance differences of functional groups between different fertilization treatments.Additionally,combined with soil physicochemical properties and bacterial community characteristics,we explored the key soil environmental factors that changed the structure and functional characteristics of the soil bacterial community.Compared with that under CK,the soil bulk density(BD)under the MV returning incorporated with reduced chemical fertilizer treatment was decreased,whereas soil organic carbon(SOC),total nitrogen(TN),total phosphorus(TP),and total potassium(TK)were increased by 12.7%-35.5%,38.2%-65.7%,66.7%-95.2%,and 20.3%-31.6%,respectively.Compared with that under the F100 treatment,the Sobs index and Shannon diversity index of the bacterial community under the MV returning incorporated with reduced chemical fertilizer were decreased,and the Sobs index and Shannon diversity index were significantly positively correlated with BD(P<0.05)but significantly negatively correlated with SOC and TN(P<0.05).Compared with that under the F100 treatment,the relative abundances of Firmicutes under the MV1F80 and MV2F60 treatments were significantly increased by 82.2%and 67.4%(P<0.05),but the relative abundances of Acidobacteria were significantly reduced by 32.6%and 40.5%(P<0.05),respectively.The relative abundance of Actinobacteria under the MV2F60 treatment was significantly increased by 30.0%(P<0.05)compared with that under the F100 treatment.According to RDA analysis,soil SOC,TN,and TK were the main soil environmental factors that significantly affected bacterial community(P<0.05).Compared with that under CK and the F100 treatment,the abundance of functional groups of chemoheterotrophy,nitrogen fixation,fermentation,and ureolysis under the MV returning incorporated with reduced chemical fertilizer treatment were improved,whereas the abundance of functional groups of animal parasites or symbionts,all human pathogens,and human pathogen pneumonia were reduced,particularly under MV1F80 and MV2F60.To summarize,the long-term MV returning to the field incorporated with reduced chemical fertilizer improved the soil physical and chemical properties,thus changing the structure and functional characteristics of the soil bacterial communities,contributing to the improvement in the soil fertility,stability,and health of micro-ecosystems in paddy fields,thus ensuring the green and sustainable development of regional agriculture.